This invention relates generally to hand tools and in particular to nail driving devices.
Nail driving tools have been proposed including a nail guide member for supporting a nail being driven and a ram member for transmitting nail driving forces to the nail. These tools were generally employed to drive in nails at inaccessible locations and to prevent damage to the surface surrounding the nail by the hammer blows. Fundamentally, a nail driving tool serves to isolate the hammer from the nail and the area surrounding the nail, while concurrently transmitting the force of the hammer impact to the nail head in a controlled manner.
If the user of a nail driving tool is unable to see the nail or to gauge the depth to which it has been driven, he may "overdrive" the nail. Overdriving the nail will result in damage to the nailed surface and/or render the fastening function of the nail ineffectual.
Nail driving tools have been proposed which were provided with mechanical stops to prevent overdriving, as illustrated by U.S. Pat. Nos. 4,054,237 and 2,657,382. These nail driving tools were intended to drive nails to a given depth. If a different nail depth was desired, modification or replacement of the mechanical stop was necessary.
Other proposed nail driving tools were provided with visual indicators to indicate the position of the ram member within the guide member. This type of nail driving tool is disclosed in U.S. Pat. Nos. 1,772,950 and 2,672,610. Nail driving tools employing indicia could only indicate discreet ram positions and if the marks were numerous, confusion could easily result.
The nailing depth accuracy of the above-mentioned nail driving tools would be sensitive to the nail head dimensions for in these tools, the depth to which a nail was driven was partly dependent upon the shape of and/or the thickness of the nail head. The thicker the nail head, the deeper the nail would be driven in.
A proposed nail driving tool disclosed in U.S. Pat. No. 3,061,835 included a guide formed by separable jaws which when separated allowed partial viewing of the nail as it was initially driven; however, as the nail head approached the nailing surface, the jaws obscured the nail head making it difficult to determine nailing depth. In general, this tool would be complex and expensive to manufacture. Moreover the presence of externally moving parts would render the use of the tool cumbersome.
In certain circumstances, for example the installation of aluminum siding, the ability to control the depth to which the nail is driven is especially important. Overdriving the nail will usually cause the nail head to pierce the siding. More importantly, the nail head should not ever be driven into contact with the siding in order to allow for thermal expansion and attendant siding movement. Nailing of the aluminum siding is thus very critical.
The prior suggested nail driving tools are not adaptable for use in this application. The inability to view the nail is detrimental to their use. Nail driving tools employing indicia on either the ram or the guide member would lack the flexibility needed for this nailing application.